30-seconds-of-code/snippets/RGB-to-hexadecimal.md

RGB to hexadecimal

Convert given RGB parameters to hexadecimal string using bitwise left-shift operator.

const rgbToHex = (r, g, b) =>
  ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');
// rgbToHex(255, 165, 1) -> 'ffa501'

Think the RGB values as binary, the max value for each will be 255 in decimal and 11111111 (8-bit) in binary. So, the left most side in hexadecimal form is for red value, middle part is green, most right side is blue, as you probably already know. To summarize it over orange rgb(255, 165, 1), #ffa501 color.

                 255      165      1
  (r << 16)   11111111 00000000 00000000
+ (g << 8)    11111111 10100101 00000000
+ (b)         11111111 10100101 00000001

toString(16)     ff       a5       01

We simply moving values to their appropriate locations. padStart(6, '0') is needed for leading left most zero characters.